The present invention specifically relates to improvements in air bags for use in an occupant safety restraint system.
More specifically, the present invention relates to an air bag and air cushion assembly used within such system. While the present invention has direct application for use in a driver side air bag module, the invention is also suited for use in passenger side air bag modules.
FIG. 1 is illustrative of a typical air bag module or assembly 20 such as a driver side air bag module which is attached to the steering wheel 22. The steering wheel includes a bracket 24 for securing the module. The module comprises a decorative forward cover 28 and a housing 32 secured by various screws 35 and rivets 37. An air cushion 40 is positioned between a retaining ring 34 and housing 32, shown in greater detail in other FIGUREs. Only a small portion of the air bag is shown in FIG. 1. The front cover 28 is secured to the housing 32, or other component of the module 20 by any number of techniques and the housing is secured to the brackets by bolts 39. As an example, the cover 28, which is fabricated of a flexible plastic material, may include a circumferential groove 42 that snaps onto a flange 44 of the housing 32. A gas generator 30 may be attached to the housing 32 and extends partially therein. In operation and in response to a signal indicative of a crash situation, the gas generator 30 generates a quantity of inflation gas 31 which is communicated through an opening 38 in the housing 32 to the air cushion 40. In response to the inflation forces generated by the air cushion, the front cover 28, along predetermined tear lines 42, opens permitting the cushion to fully expand and protect the occupant. FIG. 2 schematically illustrates an assembled module. FIG. 2 also illustrates the folded cushion 40 positioned within its housing 32. FIG. 3 illustrates a cross-sectional view of a typical partially inflated cushion 40. The cushion having two portions sewn together at a peripheral seam, comprises an outer layer of woven nylon 46 coated with a layer of rubber 48. The nylon layer is typically constructed of nylon 6.6 or nylon 6 and the coating layer 48 is typically constructed of neoprene, silicone or polycarbonate. The air bag includes a central opening 50 about which are placed rings of rubber material 52, and nylon to reinforce the opening 50.
Methods of folding the air cushion 40 such that its folded size is able to fit within the housing 32 and front cover 28 are known in the art. Suffice it to say, the air cushion 40 is folded in an acceptable manner shown schematically in FIG. 2. During the process of folding the air bag 40 and attaching the decorative cover 28 thereabout, it is difficult to maintain the air bag in its folded shape since the air bag has a tendency to billow outwardly from the housing 32 requiring considerable effort to maintain the air cushion 40 in its folded orientation while the cover 28 is being attached to the module 20. In addition, because of the inherent springiness of the air bag or cushion 40 after assembly, the cushion 40 tends to outwardly deform the frontal area 56 of the cover creating a substantial bulge therein. This bulge is often referred to as "proudness". This proudness detracts from the appearance of current air bag modules and is objectionable to both the designer and the consumer.
It is an object of the present invention to provide an air bag module having an improved appearance. A further object of the present invention is to provide for efficiencies in the manufacture of air bag modules and in particular air cushions. A further object of the present invention is to provide an air bag module having a reduced size.
Accordingly the present invention comprises: a method, as well as the resulting air bag, of reducing the size of the air bag and associated module by applying a combination of pressure and heat to the air bag in its initially folded configuration in a manner to cause the air bag material to achieve a set.
Many other objects and purposes of the invention will be clear from the following detailed description of the drawings.